Theftproof electric lamp



' April 26, 1938. D, sHg-ARER 2,115,500

THEFTPROOF ELECTR I0 LAMP Filed Aug. 2, 1937 $.27. 5. INVENTOR.

BY 6%? www ATTORNEYS y UNITED STATES o sonsis made impossible ordifiicult.

Patented Apr. 26, 1938 PATENT OFFICE nmc'rnro mm David Shearer, Battle Creek, Mich. Application August 2, masses 150,913 f 16 Claims. (01. 176-31) The main objects of my invention are: First,to provide a theft-proof plug and socket connection forelectric'lamps, fuses, etc. a 3

Second, to provide a device of the typede- 5 scribed which iseitceedingly simple in nature but unfailingly effective in operation. i Third, to provide a device of the typedescribed which is adapted to lock a lamp or other threaded plug element to prevent unauthorized removal of the same, or accidentalbreaking of the elec-,

trical connection due tobecoming loosened under vibration, but whlch is also capable of being readily and simply removed by authorized persons.

Fourth, toflprovide a device of the type described having a minimum of parts and operative by a binding or, clutching action to securely lock a lamp or other threaded plug element in a threaded socket. i i Further 2 objects relating to details and economies of my invention will definitely, appear from the description to follow. The invention is, defined in the claims. 3 1 I H A structure embodying the features of my invention is illustrated in the accompanying drawing, wherein: o t a o Fig. 1 is a fragmentary view in'transverse vertical section illustrating a lamp and socket assembly provided with the locking, means of, my '0 invention. a;

Fig. 2 is a fragmentary view of a lamp partially broken away and in section on line 2-4 of Big. 1, further illustrating mylinvention. i

Fig. 3 is a view illustrating types of keys which maybe employed to releasetheplug and socket locking connection of myiinvention, the same being shown in section one line correspondingto line H of Fig. 1.

Fig. 4 is a view time a Fig.1, of a slightly modified embodiment 'of my invention.)

Fig. 5 is a detail view partiallybrokenaway and in section to illustrate more clearly the lrolcking ring or; element of the, modification of g4. w 5' Various types of devices have hitherto been proposed for the purpose of locking the threaded plug of a lamp, fuse',,.or other elementin a similarly thread socket whereby removal of the lamp, fuse orother element by unauthorizedpersuch kno'wn theft-proof devices have been open to the objections either of being ineiiectivei for the purpose or of being too complicated in strucmm to permit thelnmanufacture and sale at u a desirable price,for they have beenof a nature However,

such that complete destruction of the lamp, tuse,

or the connection as a. whole has been necessary in order to remove and replace .a burned lamp or fuse. My invention embodies improved provisions for a lamp connection of thefamiliar plug and socket type, which require a minimum oifalteration of the said plug from] its ordinary form, since it adds merely a single locking or clutch ring to the usual number of parts. Moreover, the construction of my invention is advantageous in that it allows the plug to be removed from the socket by authorized'persons through the use of a simple key or declutching device. Such keys may be supplied at small cost withfeaeh installation of lamps equipped 15 with my locking provisions. e

Referring to the drawing the reference numeral Lindicates the usual hard rubber, flber,

' or other suitable housing of a lamp mounting wherein the metallic socket 2 is fixedly mounted to an insulating base I.

ing threads impressed therein to receive the.

threaded plug or cap 5 of the lamp 8. Although I have shown a conventional ,lampelement, it

will be understood that a fuse. or other similarly} mserta'ble inclement be .eqtlflllly well provided with the locking details of [my invention.

Adjacent the tip of plug I, one or more of the threads is cut away or omitted" and a longitudinal abutment I formed therein. An annular retaining shoulder I is. provided a on the end of the plug to retain the locking ring 0, to be hereinafter described and to cooperate with'the same and the H threads to eifect a firm frictional locking actiom The said locking ring consists of a spiral ele-. ment of round wire stock of suiflcient length to loosely embrace unthreaded orrecessed portion ,itscross section issuch as'to complement the 5 threads. 1

When the p us is screwed into socket 2, the end -i i oi ring l'willengage abutment 'lwh'ereby the ring ,formacontinuationv of the thread jil immediat ly; adjacent the abutment 5 andthe ring fwilhbethreadedwith the plug in r i the socket. flowe'yerpupon reverse rotation of the plug, through the first approximately 360,

abutment 'I will'move away from end H of the ring and-continued rotation inreverse direction A'centralf terminal 4 a I is mounted on the base in the usual manner, the socket 2 providing an annular terminal havwill cause the ring to become wedged between annular shoulder I and the threads on the plug adjacent recess i2. Since rotation of the plug relative to the ring has destroyed the alinement of the ring with the plug threads, any attempt to rotate the plug and ring together when they are out oi alinement will cause the ring to frictionally engage the socket threads and bind against the same. Accordingly, on further reverse rotation, the ring will bind between the socket threads and shoulder I and prevent rotation of the plug in that direction. Removal of the plug is thus effectively prevented. In order that the lamp may be removed, it will be apparent that the ring must be restrained from substantial movement relative to the plug when the same is initially rotated, or,.-'in other words, the ring must be restrained so as to remain in line with the plug threads and-move with the plug from the beginning of the reverse rotation of the latter.

My invention contemplates a simple provision in the form of a key element adapted to maintain this relation of the parts. The said element consists of a pin it carried on a handle member I! and suitably curved as indicated in Fig. 2, whereby it is capable of being conveniently inserted in an elongated hole It which is drilled or formed transversely of the plug threads 5. The said hole is so positioned that when the pin is fully inserted therein the end thereof projects in the space between the ends ii, I! of ring 9, as illustrated in Fig. 1. Therefore, when the plug is rotated in counterclockwise direction, the ring end I! will engage pin it; the result is that, with the ring constituting a continuation of the plug thread and restrained from substantial movement relative to the plug, it readily threads therewith out of the' socket. No binding or clutching action is created.

In order to render removal of the lamp by unauthorized persons more difllcuit, I contemplate forming key pin it of an unusual cross section, such as is illustrated at a, lib in Fig. 3. By this additional provision, it is impossible to with- .draw the lamp unless the proper key is possessed by persons desiring to withdraw the same.

It is frequently desirable to unscrew the lamp partially in order to separate the central contacts and interrupt the'circuit. My invention, in a modified form, contemplates provisions whereby this will be made possible, the same being illustrated in Figs. 4 and 5. In order to produce a structure wherein the lamp plug may be rotated to a sumcient extent to break the contact thereof with contact 4, I form recess i 2 of sufiicient extent longitudinally of the plug to allow the plug to rotate relative to the wedged ring 8 after the plug threads have disengaged from the socket threads. Of course, the ring binds between shoulder I and the socket thread to prevent removal of the plug. However, the recess is sumciently long to permit rotation of the plug without locking itself against angular movement, i. e., to disengage the plug threads from the socket threads.

In order to prevent wobbling of the plug in the socket when it is loose for rotative movement as described, but prevented from axial movement, I maintain the diameter of the plug at ill equal to the root diameter of the plug threads so that the crest of the socket threads will rest thereon and aline the plug in the socket.

To further the binding effect, I may, if desired, provide teeth or notches I! in the outer periphcry of ring 8, said teeth furnishing an increased gripping eflect against the socket threads to prevent rotation of the ring should the same come into alinement with the socket threads- However, it will be apparent that the teeth may be omitted, since the main factor in producing the locking action is the frictional clutching effect of spiral ring I when out of alinement with the socket threads. To remove the plug, the ring is declutched by a key It in the mannerdescribed above.

In the embodiment illustrated in Fig. 4, it is apparent that not only are provisions made for breaking the 'circuit by separating the central plug and socket contacts, but the lamp or bulb may be rotated indefinitely, which is desirable to prevent damaging of weak or old plugs or sockets likely to be injured if rotative force is applied to the same once the plug has become locked in the socket.

I have shown and described a spiral ring of circular cross section. However, my invention is not limited in this respect and rings of various other cross sections may be employed if desired. Likewise, the material of which the ring is made is relatively unimportant and a matter of choice. Steel, brass, bronze or other suitable substances are quite satisfactory.

From the foregoing, the operation and advantages of my construction should be clear. It is simple in nature and unfailing in operation, and moreover the locking provisions may be easily rendered inoperative by authorized persons. It is not necessary to destroy the lamp or fuse to which they are applied in order to remove the same. My invention requires only slight changes in the existing well known lamp plug to adapt the same to receive the locking ring of my in vention and obviously lamps, fuses, etc. provided with the provisions of my invention may be cheaply manufactured for marketing at a price little, if at all, greater than the price of elements not equipped with the said provisions.

I have illustrated and described my improvements in embodiments which are very practical. I have not attempted to illustrate or describe other embodiments or adaptations as it is believed this disclosure will enable those skilled in the art to embody or adapt my improvements as may be desired.

Having thus described claim as new and desire Patent is:

1. In a theft-proof electric lamp or similar element having a threaded plug insertable in a threaded socket, the threads of said plug terminating in spaced relation to an end thereof to provide a circumferential recess, said plug thread terminating at one side of the recess in the form of an abutment, a spiral locking ring loosely encircling said plug in said recess, said ring having circumferentially spaced ends oneof which is adapted to engage said abutment when the plug is rotated in one direction and form a continuation of the plug thread, whereby the ring screws into the socket with the plug, said plug having an annular shoulder adjacent said recess adapted to engage the other end of said locking ring when the plug is rotated in the other direction to wedge the ring against said shoulder and the socket threads, said plug having a longitudinal hole therein adapted to receive an unlocking key to restrain the ring into a'position in'alinement with the plug thread permitting rotation of the plug in said other direction.

my invention, what I to secure by Letters adapted to engage threaded socket. the threads or said plug termi' nating inspaced relation to an end thereof to oi! an abutment, a spiral locking ring loosely 'encircling said plug in said recess, said ring having circumferentially spaced ends one of which is adapted to engage said abutment when the plug is rotated in one direction and form a continuation of the plug thread, whereby the ring screws into the having an annular shoulder adjacent said recess the other end of said locking ring when the plug is rotated in the other direction to wedge the ring against said shoulder and the socket threads.

i 3. In a theft-proof electric lamp or similar element having a threaded plug insertable in a nating in spaced relation to an end thereof to provide a circumferential recess, said plug thread terminating at one side ofthe recess in the form ofan abutment, a spiral locking ring loosely encircling said plug in said recess, said ring having circumferentially spaced ends one of which is adapted to engage said abutment when the plug is rotated in one direction and form a continuation of the plug thread, whereby the ring screws into the socket with the plug, said plug having a projection adjacent said recess adapted to engage the other end of said locking ring when the plug is rotated in the other direction to wedge the ring against said projection and the socket threads; said plug having a longitudinal hole therein adapted to receive an unlocking key to restrain the ring into a position in alinernent with the plug threadpermitting rotation of the plug in said other direction.

4. In a theft-proof electric lampor similar ele-v ment having a threaded plug insertable in a threaded-socket, the threads of said plug terminating in spaced relation to an end thereof to provide a circumferential recess, said plug thread terminating at one side of the recess in the form of an abutment, a spiral locking ring loosely encircling said plug in said recess, said ring having circumferentially spaced ends one of which is adapted to engage said abutment when the plug is rotated in one direction and form a continuation of the plug thread, whereby the ring screws into the socket with the plug, said plug having a projection adjacent said recess adapted to engage the other end of said locking ring when the plug is rotated in the other direction to wedge the ring against said projection and the socket threads.

5. In a theft-proof electric lamp or similar element having a threaded plug insertable in a threaded socket, the plug being conformed at its inner end to provide a circumferential recess and an abutment, said plug thread terminating at the recess in the form of an abutment, a spiral locking ring encircling said plug in said recess, said ring having spaced ends one of which I is adapted to engage said abutment when the plug is rotated in one direction and form a continuation of the plug thread, said plug having an an-' nular shoulder adjacent said recess adapted to engage the other end oi! said locking ring when the plug is rotated in the other direction to wedge the ring against said shoulder and the socket threads. 1

6. In a theft-proof electric lamp or similar element having a threaded plug insertable in a withdraw the same to socket with the plug, said plugthreaded socket, the threads 01 said plug termicooperating 3 threaded socket, the plug being conformed at its-inner endrto provide a circumferential recess, locking ring encircling said plug in said recess, we plug. having'an annular shoulder adjacent saidrecess adapted to wedginglyengage said look-'- ing ring when the plug is rotated in a direction to wedge the ring agains said shoulder and the socket threads.

I. In an anti-theft screw threaded plug adapted to be screwed into a threaded socket, a spiral locking ring of round spring stock having circumferentially spaced ends, said plug having an annular end shoulder and a recessadiacent said shoulder with the plug threads terminating at an abutment adjacent said recess on the side thereof opposite said shoulder, said ring encircling said plug in said recess and cooperating with said shoulder and the socket threads to prevent unauthorized removal of the plug.

8. In an anti-theft screw threaded plug adapted to be screwed into a threaded socket, a spiral locking ring of round spring stock having spaced ends. said plug having an annular end shoulder and a recess adjacent said shoulder, said ring encircling said plug in said recess and cooperating with said shoulder and the socket threads to prevent unauthorized removal of the plug.

9. In an anti-theft electrical connection including a screw threaded plug member adapted to be screwed into a threaded socket member, a spiral locking ring of round spring stock having circumferentially spaced ends, one of said members having an annular shoulder and an unthreaded recess adjacent said shoulder, said ring encircling said plug and lying in said recess and with said shoulder and the threads on the other of said members to prevent unauthorized removal oi! the plug.

10. In an anti-theft electrical connection including a screw threaded plug member adapted to be screwed into a threaded socket member, a spiral locking ring having spaced ends, one of said members having an abutment and an un-. threaded recess adjacent said abutment, said ring encircling said plug and lying in said recess and cooperating with said abutment and the threads on the other oi. said members to enable the-plug and ring to be screwed into the socket member and to prevent unauthorized removal of the plug.

11. In an electrical element of the threaded plug type adapted to be screwed into a threaded socket, said plug having an annular recess of substantial width adjacent an end thereof, a locking ring having spaced ends encircling saidplug in the recess therein. and loose with reference to said plug and socket, said ring being formed of spring stock and adapted to wedgingly engage said plug and socket after-predetermined rotation of said plug to prevent unauthorized removal of the latter, and an abutment on said plug engageable with one end of said ring to rotate the ring with said plug to insert the plug and ring in the socket, said ring forming a continuation of the plug threads cooperable with saidsocket threads during said last named movement.

12. In an electrical element of the threaded plug type adapted to be screwed into a threaded socket, said plug having an annular recess adjacent an end thereof, a locking ring having spaced ends encircling said plug in the recess therein and loose with reference to said plug and socket, said ring being adapted to wedgingly engage said plug and socket after predeterminedable with one end oi said ring to rotate the ring with said plug to insert the plug and ring in the socket, said ring forming a continuation or the plug threads cooperable with said socket threads during said last named movement. v

13. In an electrical connection including a threaded plug member adapted to be screwed into a threaded socket member, one of said members having an Y annular recess of substantial width adjacent an end thereof, a locking ring loosely mounted relative to said members and encircling said plug member in said recess, said ring being adapted to wedgingly engage said members after predetermined rotation of said plug member to prevent unauthorized removal oi the latter, and means on said plug member engageable with said ring to rotate the ring with said plug member to insert the plug member and ring in the socket.

14. In an electrical connection including a threaded plug member adapted to be screwed into a threaded socket member, one of said members having an annular recess of substantial width adjacent an end thereof, a locking ring loosely mounted relative to said members and encircling said plug member in said recess, said ring being adapted to wedgingly engage said members after predetermined rotation of said plug member to prevent unauthorized removal of the latter.

15. In a theft-proof plug having threads engageable in a threaded socket, means for locking said plug in said socket comprising a spiral looking ring oi spring stock adapted to wedgingly engage said plug and socket upon rotation oi. the plug in one direction to prevent removal of the same, said ring having spaced ends, and means for rendering said locking ring inoperative, comprising a key, said plug having a hole receiving said key, said key being movable with said plug when the latter is rotated and coasting with one of said locking ring ends to prevent substantial relative movement of the ring with reference to said plug.

16. In a theft-proof plug having threads engageable in a threaded socket, means for locking said plug in said socket comprising a spiral locking ring adapted to wedglngly engage said plug and socket upon rotation of the plug in one direction to prevent removal of the same, and means for rendering said locking ring inoperative, comprising a key engageable with said plug and movable with said plug when the latter is rotated, said key coacting with said locking ring to prevent substantial relative movement thereof with reference to said plug.

DAVID SHEARER. 

